You must be knowing some friends who eat a lot more than you but still continue to remain in shape. And then there are people who are all the time struggling to remain in shape. These patterns are partly related to metabolism rate.
This determines how many calories are burned by our bodies. With a high metabolism rate, our bodies will burn more calories during rest and also during activity. Those having higher metabolic rate will need more ?calories to keep their body weight and this explains why some people eat more than others and still remain slim.
On the other hand, someone with slower metabolism will burn less calories during resting or activity and as a result has to limit the calories eaten with food to avoid becoming obese.
Research has also extensively concluded that our daily energy expenditure is dependent on different factors like our genetics, age, and the level of physical activity.  A research published in the The New England Journal of Medicine showed that the weight gain is a result of reduced energy expenditure in children born to overweight mothers.  More research has shown that a low metabolic rate is a high risk factor for weight gain. 
Let us see what is metabolism, what role in plays in keeping us slim or making us fat. How metabolism is related to weight loss. Is it possible to speed up metabolism rate with exercise, foods and drugs? Or is it so that the whole metabolism rate is a myth and the weight loss is a result of calorie deficit diet?
What is Metabolism?
Metabolism is actually the name given to series of chemical transformations happening in human body cells with the main purpose of converting food to energy for consumption by human body.  And metabolic rate is the speed at which our bodies burns calories to produce energy.
Medical research has shown that some people are predisposed to have higher metabolism.
Human body primarily burns calories in three ways.
First of all our bodies need a minimum metabolism rate to keep our bodies working at resting. This is called BMR which stands for basal metabolic rate. This rate is mostly determined by our genes
Then our bodies burn calories during the day to day activities we do. And finally we can force our bodies to speed up metabolism by burning calories with exercise.
Metabolism and Weight Control
Metabolism rate is determined only partly by genes. However being overweight can not be entirely attributed to slower metabolic rate. The rising epidemic of obesity is the result of changes in our dieting patterns and reduced physical activity over a period of time.
Our bodies are programmed to store excess calories as fat cells. Therefore, whether we have slow or high metabolic rate, if we eat in excess, then the calories will accumulate over a period of time and we will get overweight. Our bodies also treat the absence of lack of food as starvation and slow down our BMR. This partly explains why losing weight is so hard.
The biggest contributor to your weight loss effort will be your diet. For example, you will increase your weight by about 9 pounds a year if you eat an excess apple every day. You can lose 6 pounds over a period of one year by giving up one favorite dessert of yours every week on one day only.
In brief we can conclude that metabolism and weight loss are closely related but metabolic rate also has a genetic component. But it is not the sole factor for your weight gain. But you surely can burn more calories than your genetics permit by increasing physical activity. And when you couple this with a calorie deficit diet, you have an authentic recipe for weight loss.